[PATCH v19 00/17] KVM RISC-V Support

Anup Patel anup.patel at wdc.com
Mon Jul 26 22:54:33 PDT 2021

This series adds initial KVM RISC-V support. Currently, we are able to boot
Linux on RV64/RV32 Guest with multiple VCPUs.

Key aspects of KVM RISC-V added by this series are:
1. No RISC-V specific KVM IOCTL
2. Minimal possible KVM world-switch which touches only GPRs and few CSRs
3. Both RV64 and RV32 host supported
4. Full Guest/VM switch is done via vcpu_get/vcpu_put infrastructure
5. KVM ONE_REG interface for VCPU register access from user-space
6. PLIC emulation is done in user-space
7. Timer and IPI emuation is done in-kernel
8. Both Sv39x4 and Sv48x4 supported for RV64 host
9. MMU notifiers supported
10. Generic dirtylog supported
11. FP lazy save/restore supported
12. SBI v0.1 emulation for KVM Guest available
13. Forward unhandled SBI calls to KVM userspace
14. Hugepage support for Guest/VM
15. IOEVENTFD support for Vhost

Here's a brief TODO list which we will work upon after this series:
1. SBI v0.2 emulation in-kernel
2. SBI v0.2 hart state management emulation in-kernel
3. In-kernel PLIC emulation
4. ..... and more .....

This series can be found in riscv_kvm_v19 branch at:

Our work-in-progress KVMTOOL RISC-V port can be found in riscv_v8 branch
at: https//github.com/avpatel/kvmtool.git

The QEMU RISC-V hypervisor emulation is done by Alistair and is available
in master branch at: https://git.qemu.org/git/qemu.git

To play around with KVM RISC-V, refer KVM RISC-V wiki at:

Changes since v18:
 - Rebased on Linux-5.14-rc3
 - Moved to new KVM debugfs interface
 - Dropped PATCH17 of v18 series for having KVM RISC-V in drivers/staging

Changes since v17:
 - Rebased on Linux-5.13-rc2
 - Moved to new KVM MMU notifier APIs
 - Removed redundant kvm_arch_vcpu_uninit()
 - Moved KVM RISC-V sources to drivers/staging for compliance with
   Linux RISC-V patch acceptance policy

Changes since v16:
 - Rebased on Linux-5.12-rc5
 - Remove redundant kvm_arch_create_memslot(), kvm_arch_vcpu_setup(),
   kvm_arch_vcpu_init(), kvm_arch_has_vcpu_debugfs(), and
   kvm_arch_create_vcpu_debugfs() from PATCH5
 - Make stage2_wp_memory_region() and stage2_ioremap() as static
   in PATCH13

Changes since v15:
 - Rebased on Linux-5.11-rc3
 - Fixed kvm_stage2_map() to use gfn_to_pfn_prot() for determing
   writeability of a host pfn.
 - Use "__u64" in-place of "u64" and "__u32" in-place of "u32" for

Changes since v14:
 - Rebased on Linux-5.10-rc3
 - Fixed Stage2 (G-stage) PDG allocation to ensure it is 16KB aligned

Changes since v13:
 - Rebased on Linux-5.9-rc3
 - Fixed kvm_riscv_vcpu_set_reg_csr() for SIP updation in PATCH5
 - Fixed instruction length computation in PATCH7
 - Added ioeventfd support in PATCH7
 - Ensure HSTATUS.SPVP is set to correct value before using HLV/HSV
   intructions in PATCH7
 - Fixed stage2_map_page() to set PTE 'A' and 'D' bits correctly
   in PATCH10
 - Added stage2 dirty page logging in PATCH10
 - Allow KVM user-space to SET/GET SCOUNTER CSR in PATCH5
 - Save/restore SCOUNTEREN in PATCH6
 - Reduced quite a few instructions for __kvm_riscv_switch_to() by
   using CSR swap instruction in PATCH6
 - Detect and use Sv48x4 when available in PATCH10

Changes since v12:
 - Rebased patches on Linux-5.8-rc4
 - By default enable all counters in HCOUNTEREN
 - RISC-V H-Extension v0.6.1 spec support

Changes since v11:
 - Rebased patches on Linux-5.7-rc3
 - Fixed typo in typecast of stage2_map_size define
 - Introduced struct kvm_cpu_trap to represent trap details and
   use it as function parameter wherever applicable
 - Pass memslot to kvm_riscv_stage2_map() for supporing dirty page
   logging in future
 - RISC-V H-Extension v0.6 spec support
 - Send-out first three patches as separate series so that it can
   be taken by Palmer for Linux RISC-V

Changes since v10:
 - Rebased patches on Linux-5.6-rc5
 - Reduce RISCV_ISA_EXT_MAX from 256 to 64
 - Separate PATCH for removing N-extension related defines
 - Added comments as requested by Palmer
 - Fixed HIDELEG CSR programming

Changes since v9:
 - Rebased patches on Linux-5.5-rc3
 - Squash PATCH19 and PATCH20 into PATCH5
 - Squash PATCH18 into PATCH11
 - Squash PATCH17 into PATCH16
 - Added ONE_REG interface for VCPU timer in PATCH13
 - Use HTIMEDELTA for VCPU timer in PATCH13
 - Updated KVM RISC-V mailing list in MAINTAINERS entry
 - Update KVM kconfig option to depend on RISCV_SBI and MMU
 - Check for SBI v0.2 and SBI v0.2 RFENCE extension at boot-time
 - Use SBI v0.2 RFENCE extension in VMID implementation
 - Use SBI v0.2 RFENCE extension in Stage2 MMU implementation
 - Use SBI v0.2 RFENCE extension in SBI implementation
 - Moved to RISC-V Hypervisor v0.5 draft spec
 - Updated Documentation/virt/kvm/api.txt for timer ONE_REG interface

Changes since v8:
 - Rebased series on Linux-5.4-rc3 and Atish's SBI v0.2 patches
 - Use HRTIMER_MODE_REL instead of HRTIMER_MODE_ABS in timer emulation
 - Fixed kvm_riscv_stage2_map() to handle hugepages
 - Added patch to forward unhandled SBI calls to user-space
 - Added patch for iterative/recursive stage2 page table programming
 - Added patch to remove per-CPU vsip_shadow variable
 - Added patch to fix race-condition in kvm_riscv_vcpu_sync_interrupts()

Changes since v7:
 - Rebased series on Linux-5.4-rc1 and Atish's SBI v0.2 patches
 - Removed PATCH1, PATCH3, and PATCH20 because these already merged
 - Use kernel doc style comments for ISA bitmap functions
 - Don't parse X, Y, and Z extension in riscv_fill_hwcap() because it will
   be added in-future
 - Mark KVM RISC-V kconfig option as EXPERIMENTAL
 - Typo fix in commit description of PATCH6 of v7 series
 - Use separate structs for CORE and CSR registers of ONE_REG interface
 - Explicitly include asm/sbi.h in kvm/vcpu_sbi.c
 - Removed implicit switch-case fall-through in kvm_riscv_vcpu_exit()
 - No need to set VSSTATUS.MXR bit in kvm_riscv_vcpu_unpriv_read()
 - Removed register for instruction length in kvm_riscv_vcpu_unpriv_read()
 - Added defines for checking/decoding instruction length
 - Added separate patch to forward unhandled SBI calls to userspace tool

Changes since v6:
 - Rebased patches on Linux-5.3-rc7
 - Added "return_handled" in struct kvm_mmio_decode to ensure that
   kvm_riscv_vcpu_mmio_return() updates SEPC only once
 - Removed trap_stval parameter from kvm_riscv_vcpu_unpriv_read()
 - Updated git repo URL in MAINTAINERS entry

Changes since v5:
 - Renamed KVM_REG_RISCV_CONFIG_TIMEBASE register to
   KVM_REG_RISCV_CONFIG_TBFREQ register in ONE_REG interface
 - Update SPEC in kvm_riscv_vcpu_mmio_return() for MMIO exits
 - Use switch case instead of illegal instruction opcode table for simplicity
 - Improve comments in stage2_remote_tlb_flush() for a potential remote TLB
  flush optimization
 - Handle all unsupported SBI calls in default case of
   kvm_riscv_vcpu_sbi_ecall() function
 - Fixed kvm_riscv_vcpu_sync_interrupts() for software interrupts
 - Improved unprivilege reads to handle traps due to Guest stage1 page table
 - Added separate patch to document RISC-V specific things in

Changes since v4:
 - Rebased patches on Linux-5.3-rc5
 - Added Paolo's Acked-by and Reviewed-by
 - Updated mailing list in MAINTAINERS entry

Changes since v3:
 - Moved patch for ISA bitmap from KVM prep series to this series
 - Make vsip_shadow as run-time percpu variable instead of compile-time
 - Flush Guest TLBs on all Host CPUs whenever we run-out of VMIDs

Changes since v2:
 - Removed references of KVM_REQ_IRQ_PENDING from all patches
 - Use kvm->srcu within in-kernel KVM run loop
 - Added percpu vsip_shadow to track last value programmed in VSIP CSR
 - Added comments about irqs_pending and irqs_pending_mask
 - Used kvm_arch_vcpu_runnable() in-place-of kvm_riscv_vcpu_has_interrupt()
   in system_opcode_insn()
 - Removed unwanted smp_wmb() in kvm_riscv_stage2_vmid_update()
 - Use kvm_flush_remote_tlbs() in kvm_riscv_stage2_vmid_update()
 - Use READ_ONCE() in kvm_riscv_stage2_update_hgatp() for vmid

Changes since v1:
 - Fixed compile errors in building KVM RISC-V as module
 - Removed unused kvm_riscv_halt_guest() and kvm_riscv_resume_guest()
 - Set KVM_CAP_SYNC_MMU capability only after MMU notifiers are implemented
 - Made vmid_version as unsigned long instead of atomic
 - Renamed kvm_riscv_stage2_update_pgtbl() to kvm_riscv_stage2_update_hgatp()
 - Configure HIDELEG and HEDELEG in kvm_arch_hardware_enable()
 - Updated ONE_REG interface for CSR access to user-space
 - Removed irqs_pending_lock and use atomic bitops instead
 - Added separate patch for FP ONE_REG interface
 - Added separate patch for updating MAINTAINERS file

Anup Patel (13):
  RISC-V: Add hypervisor extension related CSR defines
  RISC-V: Add initial skeletal KVM support
  RISC-V: KVM: Implement VCPU create, init and destroy functions
  RISC-V: KVM: Implement VCPU interrupts and requests handling
  RISC-V: KVM: Implement VCPU world-switch
  RISC-V: KVM: Handle MMIO exits for VCPU
  RISC-V: KVM: Handle WFI exits for VCPU
  RISC-V: KVM: Implement VMID allocator
  RISC-V: KVM: Implement stage2 page table programming
  RISC-V: KVM: Implement MMU notifiers
  RISC-V: KVM: Document RISC-V specific parts of KVM API

Atish Patra (4):
  RISC-V: KVM: Add timer functionality
  RISC-V: KVM: FP lazy save/restore
  RISC-V: KVM: Implement ONE REG interface for FP registers
  RISC-V: KVM: Add SBI v0.1 support

 Documentation/virt/kvm/api.rst          |  193 ++++-
 MAINTAINERS                             |   12 +
 arch/riscv/Kconfig                      |    1 +
 arch/riscv/Makefile                     |    1 +
 arch/riscv/include/asm/csr.h            |   87 ++
 arch/riscv/include/asm/kvm_host.h       |  266 ++++++
 arch/riscv/include/asm/kvm_types.h      |    7 +
 arch/riscv/include/asm/kvm_vcpu_timer.h |   44 +
 arch/riscv/include/uapi/asm/kvm.h       |  128 +++
 arch/riscv/kernel/asm-offsets.c         |  156 ++++
 arch/riscv/kvm/Kconfig                  |   36 +
 arch/riscv/kvm/Makefile                 |   25 +
 arch/riscv/kvm/main.c                   |  118 +++
 arch/riscv/kvm/mmu.c                    |  802 ++++++++++++++++++
 arch/riscv/kvm/tlb.S                    |   74 ++
 arch/riscv/kvm/vcpu.c                   | 1002 +++++++++++++++++++++++
 arch/riscv/kvm/vcpu_exit.c              |  701 ++++++++++++++++
 arch/riscv/kvm/vcpu_sbi.c               |  173 ++++
 arch/riscv/kvm/vcpu_switch.S            |  400 +++++++++
 arch/riscv/kvm/vcpu_timer.c             |  225 +++++
 arch/riscv/kvm/vm.c                     |   96 +++
 arch/riscv/kvm/vmid.c                   |  120 +++
 drivers/clocksource/timer-riscv.c       |    9 +
 include/clocksource/timer-riscv.h       |   16 +
 include/uapi/linux/kvm.h                |    8 +
 25 files changed, 4691 insertions(+), 9 deletions(-)
 create mode 100644 arch/riscv/include/asm/kvm_host.h
 create mode 100644 arch/riscv/include/asm/kvm_types.h
 create mode 100644 arch/riscv/include/asm/kvm_vcpu_timer.h
 create mode 100644 arch/riscv/include/uapi/asm/kvm.h
 create mode 100644 arch/riscv/kvm/Kconfig
 create mode 100644 arch/riscv/kvm/Makefile
 create mode 100644 arch/riscv/kvm/main.c
 create mode 100644 arch/riscv/kvm/mmu.c
 create mode 100644 arch/riscv/kvm/tlb.S
 create mode 100644 arch/riscv/kvm/vcpu.c
 create mode 100644 arch/riscv/kvm/vcpu_exit.c
 create mode 100644 arch/riscv/kvm/vcpu_sbi.c
 create mode 100644 arch/riscv/kvm/vcpu_switch.S
 create mode 100644 arch/riscv/kvm/vcpu_timer.c
 create mode 100644 arch/riscv/kvm/vm.c
 create mode 100644 arch/riscv/kvm/vmid.c
 create mode 100644 include/clocksource/timer-riscv.h


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